//
//  TronView.swift
//  OS Vault
//
//  Author: Simon-Pierre Boucher
//  Mail: contact@spboucher.ai
//

import SwiftUI
import BigInt

/// Tron panel: USDT (TRC-20) + TRX balances, receive, send with the energy
/// burn estimate surfaced before signing, Nile/mainnet switch.
struct TronView: View {
    @EnvironmentObject var app: AppState
    @Environment(\.dismiss) private var dismiss

    enum Mode { case overview, receive, send }
    @State private var mode: Mode = .overview

    @State private var sendUSDT = true
    @State private var recipient = ""
    @State private var amountInput = ""
    @State private var prepared: TronService.PreparedTronSend?
    @State private var password = ""
    @State private var sending = false
    @State private var estimating = false
    @State private var sentTxid: String?
    @State private var errorMessage: String?

    var body: some View {
        VStack(alignment: .leading, spacing: 16) {
            header
            switch mode {
            case .overview: overview
            case .receive: receive
            case .send: send
            }
        }
        .padding(24)
        .frame(width: 470)
    }

    private var header: some View {
        HStack {
            Text("Tron").font(.title2.bold())
            Spacer()
            Text(app.tronNetwork.isTestnet ? "NILE · test" : "MAINNET")
                .font(.caption.weight(.bold))
                .padding(.horizontal, 10).padding(.vertical, 4)
                .background(app.tronNetwork.isTestnet ? Color.orange.opacity(0.25) : Color.red.opacity(0.22))
                .foregroundStyle(app.tronNetwork.isTestnet ? Color.orange : Color.red)
                .clipShape(Capsule())
            Button("Done") { dismiss() }
        }
    }

    // MARK: - Overview

    private var overview: some View {
        VStack(alignment: .leading, spacing: 14) {
            VStack(alignment: .leading, spacing: 10) {
                HStack(alignment: .firstTextBaseline) {
                    Text("USDT").font(.headline)
                    Spacer()
                    VStack(alignment: .trailing, spacing: 2) {
                        Text(TokenAmount.format(BigUInt(app.tronBalances?.usdtUnits ?? 0), decimals: 6))
                            .font(.system(size: 26, weight: .bold, design: .rounded))
                            .monospacedDigit()
                        if let fiat = fiatLine(units: app.tronBalances?.usdtUnits ?? 0, decimals: 6, symbol: "USDT") {
                            Text(fiat).font(.caption).foregroundStyle(.secondary)
                        }
                    }
                }
                Divider()
                HStack {
                    Text("TRX (fees)").font(.subheadline).foregroundStyle(.secondary)
                    Spacer()
                    VStack(alignment: .trailing, spacing: 2) {
                        Text(TronService.formatTRX(app.tronBalances?.trxSun ?? 0) + " TRX")
                            .font(.subheadline.monospaced())
                            .foregroundStyle(.secondary)
                        if let fiat = fiatLine(units: app.tronBalances?.trxSun ?? 0, decimals: 6, symbol: "TRX") {
                            Text(fiat).font(.caption).foregroundStyle(.secondary)
                        }
                    }
                }
                if let error = app.tronError {
                    Label(error, systemImage: "wifi.exclamationmark")
                        .font(.caption).foregroundStyle(.orange)
                }
            }
            .padding(14)
            .background(.quaternary.opacity(0.4))
            .clipShape(RoundedRectangle(cornerRadius: 10))

            HStack(spacing: 12) {
                Button {
                    mode = .send
                } label: {
                    Label("Send", systemImage: "arrow.up.circle.fill").frame(maxWidth: .infinity)
                }
                .buttonStyle(.borderedProminent)
                Button {
                    mode = .receive
                } label: {
                    Label("Receive", systemImage: "arrow.down.circle").frame(maxWidth: .infinity)
                }
                Button {
                    Task { await app.refreshTron() }
                } label: {
                    Image(systemName: "arrow.clockwise")
                }
                .help("Refresh")
            }

            Text("secp256k1 at m/44'/195'/0'/0/0 from your existing recovery phrase. USDT transfers burn TRX for energy (~13–27 TRX without staked energy) — the exact estimate is shown before you sign.")
                .font(.caption)
                .foregroundStyle(.secondary)

            Picker("Network", selection: Binding(
                get: { app.tronNetwork },
                set: { newValue in Task { await app.switchTronNetwork(to: newValue) } }
            )) {
                ForEach(TronService.TronNetwork.allCases, id: \.self) { network in
                    Text(network.displayName).tag(network)
                }
            }
            .pickerStyle(.segmented)
        }
    }

    private func fiatLine(units: UInt64, decimals: Int, symbol: String) -> String? {
        guard app.pricesEnabled, units > 0, let price = app.fiatPrices[symbol] else { return nil }
        let value = PriceService.fiatValue(units: BigUInt(units), decimals: decimals, price: price)
        return "≈ " + PriceService.formatFiat(value, currency: app.fiatCurrency)
    }

    // MARK: - Receive

    private var receive: some View {
        VStack(spacing: 14) {
            if let address = app.tronAddress {
                if let qr = QRCode.image(for: address) {
                    Image(nsImage: qr)
                        .interpolation(.none)
                        .resizable()
                        .frame(width: 200, height: 200)
                        .background(.white)
                        .clipShape(RoundedRectangle(cornerRadius: 8))
                }
                Text(address)
                    .font(.callout.monospaced())
                    .textSelection(.enabled)
                    .padding(8)
                    .background(.quaternary.opacity(0.4))
                    .clipShape(RoundedRectangle(cornerRadius: 8))
                CopyButton(text: address)
                Text("One address for TRX and every TRC-20 token on \(app.tronNetwork.displayName).")
                    .font(.caption).foregroundStyle(.secondary)
            }
            Button("Back") { mode = .overview }
        }
        .frame(maxWidth: .infinity)
    }

    // MARK: - Send

    private var send: some View {
        VStack(alignment: .leading, spacing: 12) {
            if let txid = sentTxid {
                sentView(txid)
            } else if let prepared {
                confirmView(prepared)
            } else {
                sendForm
            }
        }
    }

    private var sendForm: some View {
        VStack(alignment: .leading, spacing: 12) {
            Picker("Asset", selection: $sendUSDT) {
                Text("USDT").tag(true)
                Text("TRX").tag(false)
            }
            .pickerStyle(.segmented)
            TextField("Recipient (T…)", text: $recipient)
                .textFieldStyle(.roundedBorder)
                .font(.body.monospaced())
                .autocorrectionDisabled()
            if !recipient.isEmpty && !TronService.validate(address: recipient) {
                Label("Not a valid Tron address", systemImage: "xmark.circle")
                    .font(.caption).foregroundStyle(.red)
            }
            HStack {
                TextField("Amount", text: $amountInput)
                    .textFieldStyle(.roundedBorder)
                    .font(.body.monospaced())
                Text(sendUSDT ? "USDT" : "TRX").foregroundStyle(.secondary)
            }
            Text(sendUSDT
                 ? "Balance: \(TokenAmount.format(BigUInt(app.tronBalances?.usdtUnits ?? 0), decimals: 6)) USDT"
                 : "Balance: \(TronService.formatTRX(app.tronBalances?.trxSun ?? 0)) TRX")
                .font(.caption).foregroundStyle(.secondary)
            if let errorMessage {
                Text(errorMessage).foregroundStyle(.red).font(.callout)
            }
            HStack {
                Button("Back") { mode = .overview; errorMessage = nil }
                Spacer()
                if estimating { ProgressView().controlSize(.small) }
                Button("Review") { estimate() }
                    .buttonStyle(.borderedProminent)
                    .disabled(!formValid || estimating)
            }
        }
    }

    private var parsedAmount: UInt64? {
        sendUSDT ? TronService.parseUSDT(amountInput) : TronService.parseTRX(amountInput)
    }

    private var formValid: Bool {
        TronService.validate(address: recipient) && (parsedAmount ?? 0) > 0
    }

    private func estimate() {
        guard let amount = parsedAmount else { return }
        errorMessage = nil
        estimating = true
        let to = recipient.trimmingCharacters(in: .whitespacesAndNewlines)
        let usdt = sendUSDT
        Task {
            do {
                prepared = try await app.tronService.estimateSend(
                    to: to, amountUnits: amount, isUSDT: usdt)
            } catch {
                errorMessage = error.localizedDescription
            }
            estimating = false
        }
    }

    private func confirmView(_ p: TronService.PreparedTronSend) -> some View {
        VStack(alignment: .leading, spacing: 12) {
            Text("Confirm transaction").font(.headline)
            Grid(alignment: .leading, horizontalSpacing: 16, verticalSpacing: 8) {
                GridRow {
                    Text("Recipient").foregroundStyle(.secondary)
                    Text(p.recipient).font(.callout.monospaced())
                        .textSelection(.enabled)
                        .lineLimit(1).truncationMode(.middle)
                }
                GridRow {
                    Text("Amount").foregroundStyle(.secondary)
                    Text(p.isUSDT
                         ? "\(TokenAmount.format(BigUInt(p.amountUnits), decimals: 6)) USDT"
                         : "\(TronService.formatTRX(p.amountUnits)) TRX")
                        .fontWeight(.semibold)
                }
                GridRow {
                    Text("Network").foregroundStyle(.secondary)
                    Text(p.network.displayName)
                }
                GridRow {
                    Text("Est. fee").foregroundStyle(.secondary)
                    Text("≤ \(TronService.formatTRX(p.estimatedFeeSun)) TRX (burned)")
                }
            }
            .font(.callout)
            if p.isUSDT, (app.tronBalances?.trxSun ?? 0) < p.estimatedFeeSun {
                Label("Not enough TRX to cover the energy burn. Top up TRX first.",
                      systemImage: "exclamationmark.triangle")
                    .font(.caption)
                    .foregroundStyle(.red)
            }
            Divider()
            SecureField("Vault password to sign", text: $password)
                .textFieldStyle(.roundedBorder)
            if let errorMessage {
                Text(errorMessage).foregroundStyle(.red).font(.callout)
            }
            HStack {
                Button("Back") {
                    prepared = nil
                    password = ""
                }
                Spacer()
                if sending { ProgressView().controlSize(.small) }
                Button("Sign & send") { broadcast(p) }
                    .buttonStyle(.borderedProminent)
                    .disabled(password.isEmpty || sending)
            }
        }
    }

    private func broadcast(_ p: TronService.PreparedTronSend) {
        sending = true
        errorMessage = nil
        let candidate = password
        let manager = app.keyManager
        Task {
            do {
                let mnemonic = try await Task.detached {
                    try manager.unlock(password: candidate).mnemonic
                }.value
                let txid = try await app.tronService.send(p, mnemonic: mnemonic)
                password = ""
                sentTxid = txid
                await app.refreshTron()
            } catch {
                errorMessage = error.localizedDescription
            }
            sending = false
        }
    }

    private func sentView(_ txid: String) -> some View {
        VStack(spacing: 12) {
            Image(systemName: "paperplane.circle.fill")
                .font(.system(size: 38)).foregroundStyle(.green)
            Text("Transaction sent").font(.headline)
            Text(txid)
                .font(.caption.monospaced())
                .textSelection(.enabled)
                .lineLimit(1).truncationMode(.middle)
            Link("View on Tronscan", destination: app.tronNetwork.explorerTxURL(txid))
            Button("Done") {
                sentTxid = nil
                prepared = nil
                recipient = ""
                amountInput = ""
                mode = .overview
            }
            .buttonStyle(.borderedProminent)
        }
        .frame(maxWidth: .infinity)
    }
}